The present invention relates to an end dump trailer, a trailer frame assembly, a latch lift assembly for an end dump trailer, a radiused dump body and a method for forming a radiused dump body.
A semi end dump trailer is a tractor-trailer combination wherein the trailer itself contains the hydraulic hoist to lift the dump body. A typical semi end dump trailer (hereinafter “end dump trailer”) has a 3-axle tractor pulling a 2-axle or 3-axle semi-trailer, however other axle combinations are possible. The tractor is equipped with a fifth wheel connection, including a fifth wheel locking mechanism, and the trailer includes a kingpin connection or kingpin assembly at its front connecting portion. The kingpin assembly is reinforced to transfer trailer load to the tractor and to transmit torsional/twisting loads from the trailer to the tractor. A key advantage of a semi end dump trailer is rapid unloading. A key disadvantage is that the trailer can be very unstable when raised in the dumping position, limiting its use in applications where the dumping location is uneven or off level. End dump trailer units (i.e., without the tractor drive unit) are configured for on-road travel, so have size dimensions which are within government road and highway regulations (on-road size regulations). Generally, the longitudinal length of the trailer may range between about 20-48 ft. and the transverse width of the trailer will typically be between about 8 and 9 ft. for on-road travel. A length to width ratio for an end dump trailer is generally in the range of 2.5:1 to 6:1, more typically in the range of 3.5:1 and 4.5:1.
The dump bodies of end dump trailers are supported on wheeled vehicles or frames which are generally categorized as full frame, quarter frame, or frameless. For the full frame type, an end dump trailer is typically constructed with a pivoting dump body hinged at its rear end to a chassis formed as a ladder frame. A ladder frame generally consists of two parallel steel I-beams spaced apart by multiple transverse structural steel reinforcing members (often termed cross members). The I-beams themselves are formed by welding, and the cross members are welded at multiple locations between the I-beams. This creates a heavy frame, and requires significant input by skilled welders. As well, a ladder frame provides limited stability control as the dump body is raised into its dumping position.
A frame termed a “unibeam” frame system is shown in U.S. Pat. Nos. 5,611,570 and 5,722,688 to Garcia. This frame is shown with long semi trailer trucks such as used to transport containers. The frame includes longitudinal and parallel spaced vertical members (termed unibeams), each having an inverse T-cross section, welded together at their top edges with a horizontal web termed a uniflange. A plurality of transverse cross members are included between the longitudinal members. The unibeam frame has not, to inventors' knowledge, been applied in the semi end dump trailer industry. The unibeam frame has a goal to provide a frame which accommodates flexure.
The hoist system most often used on most end dump trailers is comprised of a multiple-staged telescoping hydraulic cylinder mounted at the front of the chassis and connecting to the underside or to the top front portion of the dump body. This hoist system provides little or no contribution to stability of the end dump trailer in the raised dumping position, so uneven ground conditions may lead to tipping of the trailer. To provide the required tipping angle, which can be greater than 45 degrees to horizontal (ground), the hydraulic hoist is typically formed in multiple telescoping sections of four or more sections (termed stages). The multiple telescoping sections and long stroke generally prevent dual action over the full stroke. Single action telescoping cylinders, or multiple stage cylinders without full dual action, must use gravity for some or all of the stages to lower the dump body back to the lowered, horizontal position. This slows the dump cycle for the vehicle, particularly in cold weather.
The dump bodies of end dump trailers are available in many shapes ranging from rectangular dump boxes to dump bodies with radially curved floor and/or side panels. The radially curved floor/side panels are advantageous for faster and more complete dumping of bulk materials such as gravel, sand, asphalt, and aggregate. To form a radially curved floor panel, the steel is rolled into shape. Multiple curved panels are welded together, typically transverse to the direction of unloading, to form these curved floor panels. The welded joints of these curved panels make unloading more difficult as bulk materials, particularly sticky materials such as asphalt, resist gravity movement at the panel joints. To completely unload, the angle of the dump body may need to be increased even above 45 degrees, which can cause instability, particularly if the trailer is on uneven ground or if the payload of bulk materials is not uniformly distributed or shifts during travel or unloading.
One exemplary curved panel dump body is shown in U.S. Pat. No. 3,844,616 issued to Acker. A half-elliptical dump body is formed of sheet metal, presumably steel, and three arcuate sections are joined, presumably by welding, to a pair of vertical side walls. Acker does not specify whether the three arcuate sections are formed separately and welded longitudinally the length of the body, or are formed in one piece and welded transversely to a plurality of similar shaped sections. The dump body of Acker includes exterior bolsters on the sides of the dump body, about center of the body. The bolsters extend from the top rail to almost the bottom of the body.
Other exemplary curved dump bodies are shown in U.S. Pat. No. 5,431,475 to Perry; U.S. Pat. No. 5,482,356 to Goodson, Jr.; U.S. Pat. No. 6,637,808 to Ling et al.; U.S. Pat. No. 6,623,234 to Herring et al.; U.S. Published Patent Application 2008/00181135 to Risner. U.S. Pat. No. 6,490,772 to Deckert et al. describes schematically different ways to form a curved skip body using forms, rollers, presses or clamps. U.S. Pat. No. 6,931,720 to Thompson describes a forming press to fabricate a curved dump body.
Various types of interior or exterior reinforcement members and/or under frames are provided on these curved dump bodies to provide sufficient structural stability and strength. These reinforcement members and under frames add considerable weight to the dump body and also complicate the overall methods of fabrication. As well, rolling steel to form the curved panels required complicated steel rolling equipment.
Dump trucks and end dump trailers of the type which discharge the payload from the rear end of the dump body typically include a tailgate or end dump gate closing the end of the dump body. The gate is pivotally attached at its upper end to the dump body, allowing the gate to swing open and away from the dump body as the dump body is angled upwardly with the hoist. The lower end of the dump gate is generally released from or locked against the dump body by latch mechanisms on opposite sides of the dump body's rear end. Each latch mechanism may be a simple cradle catch located on the side of the dump body's rear end with a latch pin extending horizontally on each side of the dump gate. The latch mechanism may be mechanically operated, or more typically air or hydraulically controlled with actuators located on each side. Being exterior of the dump body, and in the path of the discharging payload of bulk materials, particularly a load of sticky asphalt, these latch mechanisms become coated with payload and road materials.
Improvement is needed in many aspects of dump trucks, particularly those of the end dump trailer type.